The long-term goal of my research is to obtain an understanding of how neurons recognize each other and form specific synaptic connections. The proposed research will examine the specificity and plasticity of chemical monosynaptic connections between identified neurons in the cerebral and pleural ganglia of Aplysia. The neurons make specific monosynaptic connections within each ganglion (intraganglionic connections). and with neurons in the other ganglion (interganglionic connections). Each synaptic connection is a physiological distinct type: fast EPSP, slow EPSP, IPSP. The neurons regenerate following axotomy produced by crushing the cerebro-pleural connectives. This disrupts the interganglionic synaptic connections but not the intraganglionic connections. The neurons in both ganglia will be examined physiologically using intracellular recordings and morphologically by means of intracellular dye injection during and following axonal regeneration. I will determine if regenerating neurons re-establish synaptic connections only with their specific followers or if synapses with inappropriate neurons are formed. The physiological properties of the regenerated synaptic connections (correct and incorrect) will be determined. If correct synaptic connections are found, I will determine if they are stable or subsequently lost as the specific connections are established. The results will help elucidate the mechanisms by which central neurons regenerate and form specific synaptic contacts. I will also examine the intraganglionic connections of the same neurons in each ganglion for plastic changes in synaptic function during the regeneration process. If plastic changes are observed., I will determine the physiological and morphological bases for those changes. I will also determine if the functioning of the synapses returns to normal when the interganglionic synaptic connections are reestablished. This will provide insights into how neurons regulate their synaptic connections.